Kotlin Code Smell 29 - Taming the RegEx Beast for Cleaner Code

RegEx is a wonderful tool, we should use them carefully and not look smart.

Problem

• Readability

• Maintainability

• Testability

• Intention Revealing

Solution

1. Use regular expressions just for string validation.

2. If you need to manipulate objects, don't make them strings.

Sample Code

Wrong

val regex = "^\\+(?:[0-9a-zA-Z][-]?){6,14}[0-9a-zA-Z]$".toRegex()

Right

val prefix = """\+"""
val digit = "[0-9a-zA-Z]"
val space = "[-]"
val phoneRegex = "^$prefix(?:$digit$space?){6,14}$digit$".toRegex()

Conclusion

Regular expressions are a great tool for string validation. We must use them in a declarative way and just for strings.

Names are very important to understand pattern meanings.

If we need to manipulate objects or hierarchies, we should do it in an object way.

Unless we have a conclusive benchmark of impressive performance improvement.

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Credits

• Code Smell 41 - Regular Expression Abusers by Maxi Contieri